Smoking and hypercholesterolemia, or more specifically hyper-beta-lipoproteinemia, are well established risk factors for the early development of atherosclerotic disease. The presence of both factors augments the potential risk. The question arises, therefore, as to whether cigarette smoking has a direct effect on the plasma lipoproteins and, in particular, on the atherogenetic low density lipoproteins. In this study, the influence of cigarette smoking on the lipoprotein profile was investigated in a defined cohort of 6,543 male industrial workers aged 40-59 years, consisting of 2,434 smokers and 3,975 non-smokers. The effect of smoking on the lipoprotein profile showed no significant changes in LDL and only slight changes in the other lipoprotein fractions. Other factors, such as alcohol intake, body weight, and general life style seem to have a greater influence on HDL-cholesterol than smoking. It is concluded that smoking does not significantly alter lipid metabolism and that minor differences observed between smokers and non-smokers are due to a variety of factors, rather than a reflection of a direct metabolic relationship.